This invention relates to transparent, electrically conductive semiconductor windows and more particularly such windows which are made of treated semiconductor materials, which are transparent in the infrared spectrum, and which have good electrical conductivity.
Transparent conductive windows through which optical energy must pass and which have good electrical conductivity have utility in a number of applications. These include resistance heated windows, electro magnetic interference (EMI) shielded windows, anti-static windows and transparent electrodes for use in windows. In co-pending application Ser. No. 883,897 filed July 9, 1986, entitled TRANSPARENT CONDUCTIVE WINDOWS, COATINGS, AND METHOD OF MANUFACTURE and assigned to Northrop Corporation, the assignee of the present application, transparent conductive windows, coatings and their method of manufacture are described which employ thin conductive metal layers which are sandwiched between dielectric matching layers. The devices of this prior application afford both good electrical conductivity and transmissivity in the infrared and ultra violet ranges.
The device of the present invention affords a number of advantages over that of the aforementioned prior application. These include the capability of providing transmissivity over a greater band width; higher transmissivity for optical waves having angles of incidence away from the normal; greater mechanical durability; and greater ease and economy of fabrication.
Other known applicable prior art devices are discussed by J. L. Vossen in an article on transparent conducting films which appeared in Physics of Thin Films, Volume 9, published in 1977 by Academic Press. In this article, the use of semiconductor oxides forming transparent conductive films is discussed. It has been found, however, that semiconductor oxide substrates exhibit the shortcomings of low carrier life time, resistivity which is higher than to be desired and relatively low optical transmissivity particularly in the infrared range, as compared with the devices of the present invention.